1. Field of the Invention
The present invention relates to a system for providing caller ID services in an Internet telephony system, and more particularly to a system for providing caller ID services in an Internet telephony system which is organized by a telephone exchange and an Internet service provider's server on the side of a caller, the same on the side of a callee, and the Internet connecting between the caller-side server and the caller-side server.
2. Description of the Related Art
Recently, there has been a growing interest in telecommunications services using the Internet as a medium for real-time voice communication, since this technology promises a great reduction in the costs of long-distance telephone communications, including international calls. While several types of Internet-based telephony systems are available today, the following discussion will focus on a system having a specific structure shown in FIG. 12.
FIG. 12 is a total block diagram of a conventional system for Internet telephony services. In this system, two groups of subscriber terminals can communicate with each other, through their respective local telephone exchange systems (or local switches) and appropriate servers deployed by an Internet service provider (ISP). More specifically, the left-hand side of FIG. 12 shows the caller-side subsystem including a caller's telephone terminal 101, a telephone exchange 102, and an Internet service provider's server (hereafter, "ISP server" or "server") 103. Likewise, the right-hand side shows the callee-side subsystem including a callee's telephone terminal 107, a telephone exchange 106, and an ISP server 105. The Internet 104 is used for long distance transmission between the two servers 103 and 105. Telecommunications systems of this kind are expected to find widespread market acceptance, since they extend the benefits of Internet telephony to the users of plain old subscriber equipment.
FIG. 13 is a sequence diagram showing a procedure of connection establishment in the Internet telephony system of FIG. 12. Specifically, it depicts a situation where the telephone terminal 101 is attempting a call to the telephone terminal 107. The following paragraphs will explain the steps of this procedure, with reference to the sequence numbers (S101-S107) shown in FIG. 12.
The calling subscriber, or the caller, first dials the phone number of the server 103, which makes the telephone exchange 102 establish a connection path from his/her telephone terminal 101 to the server 103 (Step S101). To ensure that the caller is an authorized user of the Internet telephony service, the server 103 executes an authentication process, requesting the caller to enter his/her service account number and registered password (Step S102).
When the caller's authenticity is confirmed, the caller sends the callee's phone number (i.e., the number assigned to the telephone terminal 107) from the telephone terminal 101 to the server 103 (Step S103). In response to this, the server 103 searches for a telephone exchange that is linked to the callee's telephone terminal 107, and if a relevant telephone exchange is found, it further searches for an ISP server that is linked to that telephone exchange. In the present example, the server 103 identifies the server 105 as appropriate. The server 103 then sends a call reception request to the server 105 via the Internet 104 (Step S104). This call reception request contains the phone number of the callee.
Upon receipt of the request, the callee-side server 105 dials the phone number of the callee's telephone terminal 107, thereby establishing a connection path to the telephone terminal 107 (Step S105). When the connection between the two telephone terminals 101 and 107 is established, the system notifies the caller that he/she can now talk to the callee, through a voice guidance function or some other appropriate means (Step S106). The telephone terminals 101 and 107 start to communicate with each other over the Internet 104 (Step S107). During this session, the voice data is compressed by a codec for signal transmission with a reduced bandwidth usage.
Incidentally, conventional public switched telephone networks provide a service feature known as a "caller identification (ID)" service, which permits the recipient of an incoming call to determine, even before answering, the phone number from which the incoming call is being placed. To implement this feature, the caller-side local switch transmits, when processing a call request, the caller's phone number to the callee-side local switch through an inter-office trunk line (H2). The local switch on the callee's side delivers the received phone number information to the called subscriber. This caller ID service can be used in various applications, including such a service that tracks and locates a malicious caller who is threatening a subscriber.
However, the users of Internet telephony services cannot enjoy the above benefits of caller ID services. Because of the presence of the Internet 104 as an intermediate transmission medium between the telephone exchanges 102 and 106, an attempt of the callee-side telephone exchange 106 to identify the caller would end up with the phone number of the server 105, instead of that of the telephone terminal 101, which is what the telephone exchange 106 is really looking for.
As clarified above, the conventional Internet telephony systems are unable to provide users with caller ID services.